The present invention is related to Japanese patent application No. 2000-235903, Aug. 3, 2000; the contents of which are incorporated herein by reference.
The present invention relates to a misfire detection apparatus for an internal combustion engine, and more particularly, for a misfire detection apparatus that detects a misfire which occurs in an engine.
Conventionally, as a known technique of detecting an engine misfire, Japanese Patent No. 2982381 discloses performing misfire determination in a four-cylinder internal combustion engine based on a rotational speed deviation (first variation amount) between two cylinders where expansion strokes are successively made and a rotational speed deviation (second variation amount) between two cylinders 360xc2x0 CA (crank angle) ahead where expansion strokes are successively made (hereinbelow referred to as a 360xc2x0 CA difference calculation).
Further, another known technique of detecting a misfire similarly from two variation amounts is performing misfire determination based on a rotational speed deviation (first variation amount) between two cylinders where expansion strokes are successively made and a rotational speed deviation (second variation amount) between two cylinders 720xc2x0 CA ahead where successive expansion strokes are successively made (hereinbelow referred to as a 720xc2x0 CA difference calculation).
However, in the 360xc2x0 CA difference calculation, where a misfire occurs in a misfire determination subject cylinder and in a cylinder 360xc2x0 CA ahead of the subject cylinder, the rotational variation which appears in the first variation amount due to the misfire is cancelled by the second variation amount. Therefore, the misfire cannot be detected. Similarly, in the 720xc2x0 CA difference calculation, when a misfire continuously occurs in a particular same cylinder, the rotational variation due to the misfire is cancelled, and the misfire cannot be detected.
As a technique to detect such specific pattern misfire, the present inventors have proposed a technique disclosed in JP-A No. Hei 10-54295. The technique is, in an eight-cylinder internal combustion engine, calculating a rotational variation amount by cylinder for two cylinders where expansion strokes are successively made as a first variation amount, calculating a deviation between a current rotational speed and a previous rotational speed of the same cylinder as a rotational variation amount, calculating a second variation amount by dividing the rotational variation amount by the number of cylinders, and performing misfire determination based on a deviation between the first and second variation amounts.
However, in any of the above conventional techniques, as a so-called difference calculation is used for performing misfire determination based on the first variation amount and the second variation amount, where the rate of increase in the rotational speed is high at the beginning and then becomes lower upon engine start, such as during abrupt acceleration or the like, there is a possibility of erroneous determination of misfire.
For example, for misfire detection by the 360xc2x0 CA difference calculation in a six-cylinder internal combustion engine, the first variation amount is xe2x80x9cxcfx89n-1xe2x88x92xcfx89nxe2x80x9d, and the second variation amount by the 360xc2x0 CA difference calculation is xe2x80x9cxcfx89n-4xe2x88x92xcfx89n-3xe2x80x9d, as shown in FIG. 4. Note that xcfx89n represents a current rotational speed of misfire determination subject cylinder n, and xcfx89n-i, the i-times previous rotational speed of the misfire determination subject cylinder n.
As in the engine start time, in a running state where the rate of increase in the engine rotational speed is high at the beginning and then becomes lower, as the second variation amount xe2x80x9cxcfx89n-4xe2x88x92xcfx89n-3xe2x80x9d becomes greater than the first variation amount xe2x80x9cxcfx89n-1xe2x88x92xcfx89nxe2x80x9d, the difference between the first variation amount and the second variation amount (hereinbelow referred to as a final variation amount xcex94xcfx89) is large.
The problem also occurs in the second variation amount in the 720xc2x0 CA difference calculation and the second variation amount in other difference calculations.
Accordingly, in a running state where the change rate of rotational speed is high at the beginning and then becomes lower as shown in FIG. 5, the final variation amount xcex94xcfx89 becomes large by the influence of the second variation amount. For this reason, in the above conventional techniques, there is a possibility that the final variation amount xcex94xcfx89 exceeds a misfire determination level (A in FIG. 5), and erroneous determination of misfire may be made even though a misfire has not actually occurred.
The present invention has been made in consideration of the above situation, and provides a misfire detection apparatus for an internal combustion engine which does not erroneously detect misfire even in a running state where the rate of increase in the engine rotational speed is high at the beginning and then becomes lower upon engine start, abrupt acceleration or the like.
In a first aspect, a misfire detection apparatus for an internal combustion engine is provided that comprises a rotational angle signal output means for outputting a rotational angle signal at a predetermined rotational angle in accordance with rotation of an output shaft of a multiple cylinder internal combustion engine; rotational speed calculation means for calculating a rotational speed of the output shaft of the internal combustion engine in each cylinder, based on the rotational angle signal output from the rotational angle signal output means; first variation amount calculation means for calculating the rotational speed between two cylinders where expansion strokes are successively made, by using the rotational speed calculation means, and calculating a first variation amount based on the rotational speed between the two cylinders; second variation amount calculation means for calculating the rotational speed between two cylinders of the internal combustion engine by using the rotational speed calculation means, and calculating a second variation amount based on the rotational speed between the two cylinders; first misfire determination means for performing misfire determination based on the first variation amount and the second variation amount; and second misfire determination means for performing misfire determination based on the first variation amount, wherein in a running state with a possibility of erroneous misfire detection due to the second variation amount, the second misfire determination means performs misfire determination.
In this arrangement, in the running state with a possibility of erroneous misfire detection due to the second variation amount, as the second misfire determination means performs misfire determination based on the first variation amount, even in a running state where the rate of increase in rotational speed of the internal combustion engine is high at the beginning and then becomes lower, misfire determination can be performed without influence of the second variation amount, thereby erroneous misfire detection can be prevented.
Note that in the present invention, the first variation amount includes a deviation of rotational speed between successive cylinders, a ratio of rotational speed between the successive cylinder, a deviation of time required for predetermined rotation between the successive cylinders, and a ratio of time required for predetermined rotation between the successive cylinders.
Further, in the present invention, the second variation amount includes a deviation of rotational speed between two cylinders, a ratio of rotational speed between the two cylinders, a deviation of time required for predetermined rotation between the two cylinders, and a ratio of time required for predetermined rotation between the two cylinders.
In another aspect, the second variation amount calculation means calculates the rotational speed between two cylinders ahead of the first variation amount calculated by the first variation amount calculation means by a rotational angle of 360xc2x0 CA (crank angle) where expansion strokes are successively made, by using the rotational speed calculation means, and calculates the second variation amount based on a rotational speed deviation between the two cylinders.
In this arrangement, even in case of misfire determination by the 360xc2x0 CA difference calculation, in the running state with a possibility of erroneous misfire detection due to the second variation amount, as the second misfire determination means performs misfire determination based on the first variation amount, even in a running state where the rate of increase in rotational speed of the internal combustion engine is high at the beginning and then becomes lower, misfire determination can be performed without influence of the second variation amount, thereby erroneous misfire detection can be prevented.
In another aspect, the second variation amount calculation means calculates the rotational speed between two cylinders ahead of the first variation amount calculated by the first variation amount calculation means by a rotational angle of 720xc2x0 CA (crank angle) where expansion strokes are successively made, by using the rotational speed calculation means, and calculates the second variation amount based on a rotational speed deviation between the two cylinders.
In this arrangement, even if the misfire determination by the 720xc2x0 CA difference calculation, while running with a possibility of erroneous misfire detection due to the second variation amount, as the second misfire determination means performs misfire determination based on the first variation amount, even in a running state where the rate of increase in rotational speed of the internal combustion engine is high at the beginning and then becomes lower, misfire determination can be performed without influence of the second variation amount, thereby erroneous misfire detection can be prevented.
In another aspect, the second variation amount calculation means calculates the rotational speed between cylinders away from each other by an integer multiple of a crank angle as minimum-unit, obtained by dividing a crank angle necessary for one combustion cycle of each cylinder by the number of cylinders, by using the rotational speed calculation means, and calculates a value, obtained by dividing the rotational speed deviation between the two cylinders away from each other by the integer multiple of the crank angle by the integer, as the second variation amount, and the first misfire determination means performs misfire determination based on the first variation amount and the second variation amount.
In this arrangement, even in case of misfire determination by the difference calculation, in the running state with a possibility of erroneous misfire detection due to the second variation amount, as the second misfire determination means performs misfire determination based on the first variation amount, even in a running state where the rate of increase in rotational speed of the internal combustion engine is high at the beginning and then becomes lower, misfire determination can be performed without influence of the second variation amount, thereby erroneous misfire detection can be prevented.
In another aspect, the second misfire determination means performs misfire determination after the start of the internal combustion engine until the number of ignitions counted by the ignition counter becomes a predetermined number.
In this arrangement, as the second misfire determination means performs misfire determination during a predetermined period with a possibility of erroneous misfire detection due to the second variation amount after the start of the internal combustion engine, erroneous misfire detection can be prevented.
In another aspect, the second misfire determination means performs misfire determination when the second variation amount, calculated by the second variation amount calculation means based on the rotational speed of the internal combustion engine, is greater than a first predetermined value. In this arrangement, as the second misfire determination means performs misfire determination upon non-constant speed change such as the start of the internal combustion engine, the initial stage of acceleration or the like, erroneous misfire detection in the above running state can be prevented.
In another aspect, the second misfire determination means performs misfire determination when a change rate of the rotational speed calculated by the rotational speed calculation means is equal to or greater than a second predetermined value. In this arrangement, as the second misfire determination means performs misfire determination upon non-constant speed change such as the start of the internal combustion engine, the initial stage of acceleration or the like, erroneous misfire detection in the above running state can be prevented.
In another aspect, the second misfire determination means performs misfire determination from a point where the change rate of the rotational speed calculated by the rotational speed calculation means is equal to or greater than the second predetermined value to a point where the change rate of the rotational speed calculated by the rotational speed calculation means is equal to or less than a third predetermined value which is less than the second predetermined value, and thereafter, the first misfire determination means performs misfire determination.
In this arrangement, as the second misfire determination means performs misfire determination upon non-constant speed change such as the start of the internal combustion engine, the initial stage of acceleration or the like, erroneous misfire detection in the above running state can be prevented.
Further, as the first misfire determination means performs misfire determination after the misfire determination by the second misfire determination means, the precision of determination can be improved.
In another aspect, if a deviation between the first variation amount and the second variation amount is greater than a first determination level, the first misfire determination means determines that a misfire has occurred in the internal combustion engine, and if the first variation amount is greater than a second determination level, the second misfire determination means determines that a misfire has occurred in the internal combustion engine. In this arrangement, as respective misfire determination levels are set for the first misfire determination means and the second misfire determination means, a misfire can be detected with high precision.
In another aspect, the second misfire determination level is a value to detect the misfire more easily than that of the first misfire determination level. That is, where the second misfire determination means performs misfire determination, as the rotational speed of the engine is increasing, the reduction of the rotational speed due to misfire does not clearly appear. Accordingly, in this arrangement, the precision of misfire detection by the second misfire determination means can be improved by setting the misfire determination level to a value to easily detect misfire.
In another aspect, a misfire detection apparatus for an internal combustion engine is provided that comprises rotational angle signal output means for outputting a rotational angle signal at a predetermined rotational angle in accordance with rotation of an output shaft of a multiple cylinder internal combustion engine; rotational speed calculation means for calculating a rotational speed of the output shaft of the internal combustion engine in each cylinder, based on the rotational angle signal outputted from the rotational angle signal output means; first variation amount calculation means for calculating the rotational speed between two cylinders where expansion strokes are successively made, by using the rotational speed calculation means, and calculating a first variation amount based on the rotational speed between the two cylinders; second variation amount calculation means for calculating the rotational speed between two cylinders by the rotational speed calculation means, and calculating a second variation amount based on the rotational speed between the two cylinders; first misfire determination means for performing misfire determination based on the first variation amount and the second variation amount; correction means for correcting the second variation amount; and second misfire determination means for performing misfire determination based on the second variation amount corrected by the correction means and the first variation amount, wherein in a running state with a possibility of erroneous misfire detection due to the second variation amount not corrected by the correction means, the second misfire determination means performs misfire determination.
In this arrangement, even in a running state where the change rate of rotational speed of the internal combustion engine is high at the beginning and then becomes lower upon start of the engine, abrupt acceleration or the like, as the second misfire determination means performs misfire determination by using the value obtained by correcting the second variation amount, erroneous misfire detection can be prevented without influence of the second variation amount.
In another aspect, if a deviation between the first variation amount and the second variation amount is greater than a first determination level, the first misfire determination means determines that a misfire has occurred, and if the deviation between the first variation amount and the second variation amount corrected by the correction means is greater than a second determination level, the second misfire determination means determines that a misfire has occurred. In this arrangement, as respective misfire determination levels are set for the first misfire determination means and the second misfire determination means, a misfire can be detected with high precision.
In another aspect, the second misfire determination level is a value to detect the misfire more easily than that of the first misfire determination level. In this arrangement, the second misfire determination means performs misfire determination when the change rate of rotation of the internal combustion engine is high upon start, abrupt acceleration or the like. At this time, as the misfire determination level is set to the second misfire determination level lower than the first misfire determination level, the precision of misfire determination can be improved in a running state where the change rate of rotational speed of the internal combustion engine is high and a rotational variation amount is not clearly obtained.
In another aspect, the second variation amount calculation means calculates the rotational speed between two cylinders ahead of the first variation amount calculated by the first variation amount calculation means by a rotational angle of 360xc2x0 CA (crank angle) where expansion strokes are successively made, by using the rotational speed calculation means, and calculates the second variation amount based on a rotational speed deviation between the two cylinders.
In this arrangement, even in case of misfire determination by the 360xc2x0 CA difference calculation, in the running state with a possibility of erroneous misfire detection due to the second variation amount, as the second misfire determination means performs misfire determination based on the first variation amount, even in a running state where the rate of increase in rotational speed of the internal combustion engine is high at the beginning and then becomes lower, misfire determination can be performed without influence of the second variation amount, thereby erroneous misfire detection can be prevented.
In another aspect, the second variation amount calculation means calculates the rotational speed between two cylinders ahead of the first variation amount calculated by the first variation amount calculation means by a rotational angle of 720xc2x0 CA (crank angle) where expansion strokes are continuously made, by using the rotational speed calculation means, and calculates the second variation amount based on a rotational speed deviation between the two cylinders.
In this arrangement, even in case of misfire determination by the 720xc2x0 CA difference calculation, in the running state with a possibility of erroneous misfire detection due to the second variation amount, as the second misfire determination means performs misfire determination based on the first variation amount, even in a running state where the rate of increase in rotational speed of the internal combustion engine is high at the beginning and then becomes lower, misfire determination can be performed without influence of the second variation amount, thereby erroneous misfire detection can be prevented.
In another aspect, the second variation amount calculation means calculates the rotational speed between cylinders away from each other by an integer multiple of a crank angle as minimum-unit, obtained by dividing a crank angle necessary for one combustion cycle of each cylinder by the number of cylinders, by using the rotational speed calculation means, and calculates a value, obtained by dividing the rotational speed deviation between the two cylinders away from each other by the integer multiple of the crank angle by the integer, as the second variation amount, and the first misfire determination means performs misfire determination based on the first variation amount and the second variation amount. In this arrangement, even in case of misfire determination by the difference calculation, in the running state with a possibility of erroneous misfire detection due to the second variation amount, as the second misfire determination means performs misfire determination based on the first variation amount, even in a running state where the rate of increase in rotational speed of the internal combustion engine is high at the beginning and then becomes lower, misfire determination can be performed without influence of the second variation amount, thereby erroneous misfire detection can be prevented.
In another aspect, the correction means sets a correction amount to correct the second variation amount based on the running state of the internal combustion engine detected by the running state detection means, and corrects the second variation amount based on the correction amount. In this arrangement, as the correction amount to correct the second variation amount can be set in accordance with various running states of the internal combustion engine, the precision of misfire determination by the second misfire determination means can be improved.
In another aspect, the running state of the internal combustion engine detected by the running state detection means is a variation amount of the rotational speed calculated by the rotational speed calculation means. In this arrangement, as the correction amount to correct the second variation amount can be set in accordance with the variation amount of rotational speed of the internal combustion engine, the precision of misfire determination by the second misfire determination means can be improved. In another aspect, the running state of the internal combustion engine detected by the running state detection means is the second variation amount calculated by the second variation amount calculation means. In this arrangement, as the correction amount to correct the second variation amount can be set in accordance with the second variation amount, the precision of misfire determination by the second misfire determination means can be improved.
In another aspect, the second misfire determination means performs misfire determination after the start of the internal combustion engine until the number of ignitions counted by the ignition counter becomes a predetermined number. In this arrangement, as the second misfire determination means performs misfire determination during a predetermined period with a possibility of erroneous misfire detection due to the second variation amount after the start of the internal combustion engine, erroneous misfire detection can be prevented.
In another aspect, the second misfire determination means performs misfire determination when the second variation amount calculated by the second variation amount calculation means based on the rotational speed of the internal combustion engine is greater than a first predetermined value. In this arrangement, as the second misfire determination means performs misfire determination upon non-constant speed change such as the start of the internal combustion engine, the initial stage of acceleration or the like, erroneous misfire detection in the above running state can be prevented.
In another aspect, the second misfire determination means performs misfire determination when a change rate of the rotational speed calculated by the rotational speed calculation means is equal to or greater than a second predetermined value. In this arrangement, as the second misfire determination means performs misfire determination upon non-constant speed change such as the start of the internal combustion engine, the initial stage of acceleration or the like, erroneous misfire detection in the above running state can be prevented.
In another aspect, the second misfire determination means performs misfire determination from a point where the change rate of the rotational speed calculated by the rotational speed calculation means is equal to or greater than the second predetermined value to a point where the change rate of the rotational speed calculated by the rotational speed calculation means is equal to or less than a third predetermined value which is less than the second predetermined value, and thereafter, the first misfire determination means performs misfire determination. In this arrangement, as the second misfire determination means performs misfire determination upon non-constant speed change such as the start of the internal combustion engine, the initial stage of acceleration or the like, erroneous misfire detection in the above running state can be prevented.
Further, as the first misfire determination means performs misfire determination after the misfire determination by the second misfire determination means, the precision of determination can be improved.
In another aspect, provided is a misfire detection apparatus for an internal combustion engine wherein the second misfire determination means performs misfire determination for a predetermined period after the start of the internal combustion engine. In this arrangement, misfire erroneous determination due to the second variation amount can be prevented.
In another aspect, provided is a misfire detection apparatus for an internal combustion engine wherein the second misfire determination means performs misfire determination for a predetermined period after acceleration at the internal combustion engine. In this arrangement, misfire erroneous determination due to the second variation amount can be prevented.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. In the drawings: